190 
TROWBRIDGE. 
IIIGII ELECTROMOTIVE FORCE. 
will be 
from Figure 1, Plate XXV, that each tray of 
re s ts 
pon p 
insulators at their ends and at their middle. The wood between the rows of cells is 
removed, leaving a slot ; the only wood connection is therefore at the ends of the 
trays. 
LEAKAGE TO GROUND AND SIDE DISCHARGES. 
- 
The installation of such a large storage battery as I describe in this memoir presents 
many interesting problems of insulation, and it is probable that with the most perfect 
possible there is an invisible ionization betw 
and the earth. 
Such ionization becomes visible in the form of the Geissler tube shown in Figure A. 
The terminal A is connected permanently with the pole of the battery through a large 
running water resistance of several megohms ; the terminal B is connected to the 
negative pole by a spark gap. E E are condensers connected to the earth. At the 
instant the spark occurs, a brilliant side discharge occurs between E and A. At 
B 
It 
le time that these side discharges take place, a discharge passes between A and 
is evident that the capacity of the region outside the battery, the room and 
building, charges up under the difference of potential between it and the poles of the 
battery, a difference of potential which is greater than that between A and B which 
connected by the small resistance of the rarefied 
This pi 
.- 
photometric method of 
P 
th 
capacity of 
% 
C 
large condensers and also of obtaining the 
pacity of the • 
ms C and D of 
und 
cross are 
To the 
hed the 
condensers to be compared. At the instant 
of completion of the circuit with the storage 
battery under the conditions mentioned above, 
two side discharges take place from C and D, 
either to A 
B 
By bringing the li 
ght of 
disci 
able photometr 
r> 
« 
Figure A. 
pare the c 
degree of 
f 
conden 
n coin- 
to the 
accuracy obtainable by ordinary 
cult to 
photometric obse 
S 
it is dim 
obtain an estimate of the capacity of large bodies of irregular shape and of 
large extent, this method may be of u 
haustion the method does not require 
By a suitable vacuum tube and proper 
o 
umber of 
